Aircraft include structural components, such as the airframe, that generally are designed to last the service life of the aircraft. However, some components may not react to the stresses of use and the environment as expected and some aircraft may be used beyond the originally designed service life. In such cases, repair or replacement of structural components not originally designed to be repaired or replaced may cause significant downtime for individual aircraft while the affected structural components are repaired or reproduced for replacement.
For example, the F/A-18 Hornet model of aircraft was first placed into operational service in 1983. Now more than 30 years later, the majority of F/A-18 Hornet aircraft in service are operated at or beyond their originally designed service life (6,000-8,000 hours). Continued operation relies on a structured approach to inspection, maintenance, and repair that includes airframe repair and replacement. Airframe inspection, repair, and replacement are performed during cycles of heavy maintenance. During heavy maintenance, the airframe and other structural components are inspected for mechanical wear, heat damage, corrosion, and other signs of component fatigue. Though heavy maintenance commonly results in repair or replacement of some structural components, predicting which components will need repair or replacement in a particular aircraft is very difficult with current technology. Hence, maintaining the F/A-18 Hornet fleet in serviceable condition leads to new and variable demand for a large number of airframe and other structural components that were not originally designed to be repaired or replaced. Additionally, heavy maintenance results in unpredictable downtime for individual aircraft due to the variable demand for repaired or replacement components and the time to repair, reproduce, and/or replace the affected components.